package Calculator;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;

public class CalcServer {
    private DatagramSocket socket = null;

    public CalcServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        while (true){
            // 1. 读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
            // 2. 跟据请求计算响应
            String response = process(request);
            // 3. 把响应写回给客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),response.getBytes().length,
                                                            requestPacket.getSocketAddress());
            socket.send(responsePacket);
            // 4. 打印日志
            String log = String.format("[%s:%d] req: %s; resp: %s",requestPacket.getAddress().toString(),
                                    requestPacket.getPort(),request,response);
            System.out.println(log);
        }
    }

    private String process(String request) {
        // 分离
        String[] str = request.split(";");
        if(str.length != 3) return "[请求的格式出错!]";
        int num1 = Integer.parseInt(str[0]);
        int num2 = Integer.parseInt(str[1]);
        if(str[2].equals("+")){
            return num1+num2+"";
        }else if(str[2].equals("-")){
            return num1-num2+"";
        }else if(str[2].equals("*")){
            return (num1 * num2)+"";
        }else if(str[2].equals("/")){
            return (num1 / num2)+"";
        }
        return "[请求格式出错!操作符不支持!]";
    }

    public static void main(String[] args) throws IOException {
        CalcServer server = new CalcServer(9090);
        server.start();
    }
}
